Great Lakes ice cover slow to melt

Apr. 30, 2014
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Capt. Mike Davanzo commands the U.S. Coast Guard cutter Mackinaw, the largest icebreaker on the Great Lakes. Icebreaking crews have logged more than twice as many hours as in a normal season. / Eric Seals, Detroit Free Press

by Keith Matheny, Detroit Free Press

by Keith Matheny, Detroit Free Press

A relatively cool spring will give way to a colder-than-usual summer in Michigan, all because of the continuing impacts of the intensely frigid, snowy winter, scientists said. And at least one Great Lakes ice researcher thinks the domino effect could continue into a chilly fall and an early start to next winter - and beyond.

The reason is the unusually late ice cover that remains on the Great Lakes. Heading into May, the Great Lakes combined remain 26% ice-covered, with Lake Superior still more than half-blanketed in ice. By comparison, at this time last spring the lakes were less than 2% covered with ice.

The remaining levels of ice cover are amazing, said Jia Wang, an ice climatologist at the National Oceanic and Atmospheric Administration's Great Lakes Environmental Research Laboratory in Ann Arbor.

"This prolonged winter will affect summer temperatures. This summer will be cold, and then a cooler fall," he said.

In addition to wreaking havoc on the Great Lakes shipping industry and impacting fish and other aquatic species, the miles of ice cover serve as a vast, white reflector.

"All that sunlight that would normally heat up the water is just bouncing back up into space," said Jay Austin, an associate professor at the University of Minnesota-Duluth's Large Lakes Observatory, who agrees with Wang about the ice cover's impacts on this summer, but disagrees about its potential impacts on weather beyond that.

And though the impact of Great Lakes water temperatures on local weather is complex, "the two are connected to some degree," said Steve Colman, director of the Large Lakes Observatory.

"It's going to tend to be cooler," he said. "We'll likely get more fog because of colder water temperatures and warmer air masses."

The persistent ice led to "an absolutely crippling start to the shipping season," said Glen Nekvasil, vice president of the Lake Carriers Association, a trade group representing Great Lakes cargo haulers.

Icebreakers are still escorting convoys of barges hauling iron ore, cement and other products through the ice-jammed lakes, making for very slow going, he said.

One iron ore cargo ship that left port in western Lake Superior on March 23 did not deliver its first cargo on southern Lake Michigan until April 23, Nekvasil said.

"In 30 days they normally would have delivered four cargoes," he said.

Iron ore shipments in March were down 43% over last year. The large U.S. Steel plant in Gary, Ind., scaled back production early last month due to its depleted supplies of iron ore.

A normal year has Coast Guard icebreakers logging 3,000 hours breaking channels through the lakes. With at least two more weeks of icebreaking to go, crews have logged 7,000 hours this winter and spring, said Mark Gill, director of vessel traffic services for the Coast Guard at Sault Ste. Marie.

Some good news came this week when the Coast Guard was able to break through its downbound channel, a preferred, deeper shipping route that allows carriers to haul heavier loads, Gill said.

Because the ice season started so early - the first week in December - and is continuing so late, "we're going to face a real challenge here to rebuild stockpiles," Nekvasil said.

Winter's impact on the Great Lakes will lead to winners and losers in Great Lakes fish species, said Randy Claramunt, Great Lakes research biologist at the state Department of Natural Resources' Charlevoix Fisheries Research Station.

"Some of the native species - such as lake whitefish - we've found cold winters and a long duration of ice cover can actually have a positive impact," he said.

The fish spawn on near-shore, shallow, rocky reefs in the fall, and their eggs incubate all winter long, Claramunt said. Ice cover tends to keep the eggs safe from predators, he said.

Losers can include nonnative, invasive species that aren't used to such cold, harsh climates, such as the round goby and quagga mussels, he said. But "it would take decades of long winters like this to eradicate them," he said.

Biologists will be watching for potential impacts on other species that aren't native but have been around awhile, such as chinook, steelhead, coho salmon, brown trout and the smelt and alewife fish that feed the predators people fish for, Claramunt said.

"Their populations can still be up or down depending on factors such as how fast it warms up," he said.

On smaller, shallower lakes, extensive, persistent ice cover means decomposition on the lake bottom uses up the available oxygen. With less replenishment, fish die-offs can be expected, Claramunt said.

"On a lot of people's small ponds, they are going to see significant kills," he said.

The algae that many aquatic organisms rely on may thrive, said Hunter Carrick, a professor of aquatic ecosystems ecology at Central Michigan University.

"There are diatoms, a certain type of phytoplankton, that seems to grow well around ice," he said. The long winter and slow thaw "could enhance the spring diatom bloom."

With Lake Erie warming slower this spring and summer, its oxygen-starved dead zone could be lessened in intensity this year as well, Carrick said. But a major diatom bloom could counteract that, he said.

The late ice cover took a toll on waterfowl, particularly diving ducks, who couldn't find enough open water for food supplies, said Holly Vaughn, a DNR wildlife outreach technician.

"We've also noted muted swans that have starved to death for similar reasons," she said.

Biologists expect to see reduced clutch sizes as the birds enter breeding season, "fewer eggs being laid because the adults didn't have the nutrition they normally would get in the spring," she said.

The die-offs and breeding impacts, however, are not expected to significantly diminish waterfowl populations, Vaughn said.

This memorable winter and its lingering impacts makes it easy to forget that the long-term trend on lake ice is definitely downward, Colman said.

"It emphasizes the fact that, year-to-year, there is a lot of variation," he said. "It's been an amazing year."